Timber Decay Inspection Guide

How to approach a timber inspection

Start by finding the damp area and looking for the reason it has stayed wet. Then establish how far the damage goes, including concealed joist ends or timber behind fittings. That gives you a much better basis for deciding what needs repairing.

If it does not, keep looking. Water may have travelled before reaching the timber.

Check the full member, not just the exposed face

Joist ends, wall plates and beam ends can decay inside masonry pockets while the visible section still looks reasonable. Floor movement close to a wall is one clue that the concealed bearing may need opening up.

Separate historic evidence from current activity

Old beetle holes, old stains and previous chemical treatment can remain long after a problem has stopped. Fresh frass, active moisture, new fungal growth or a growing area of weakness is more significant.

Record what you find

Photographs, moisture readings and notes about the weather or recent leaks make later comparison easier. If opening-up is needed, photograph the area before and after so the extent of concealed damage is clear.

Decide what actually needs doing

The final repair may involve stopping the water source, drying, improving ventilation, retaining sound timber, strengthening a local section or replacing badly weakened material. Chemical treatment is only one possible tool, not the starting assumption.